Undefined symbol _ZN2gr12msg_accepter4postEN5boost13intrusive_ptrIN3pmt8pmt_baseEEES5_

Hi all.

I've been suffering trying to install gnuradio. I tried different versions, and different
combinations with gr-osmosdr, as I don't see a list of which versions go together.

Using, eg. gr-osmosdr.so.0.2.0 and gnuradio-3.8.4.0, which I have compiled successfully
on my Slackware64-current system, I get an error at run-time:

Executing: /usr/bin/python3 -u /usr/local/projects/rf/gnuradio/VHF_NBFM.py

Traceback (most recent call last):
File "/usr/local/projects/rf/gnuradio/VHF_NBFM.py", line 40, in <module>
import osmosdr
File "/usr/lib64/python3.9/site-packages/osmosdr/__init__.py", line 25, in <module>
from .osmosdr_swig import *
File "/usr/lib64/python3.9/site-packages/osmosdr/osmosdr_swig.py", line 13, in <module>
from . import _osmosdr_swig
ImportError: /usr/lib64/libgnuradio-osmosdr.so.0.2.0: undefined symbol: _ZN2gr12msg_accepter4postEN5boost13intrusive_ptrIN3pmt8pmt_baseEEES5_

c++filt translates that symbol to gr::msg_accepter::post(boost::intrusive_ptr<pmt::pmt_base>, boost::intrusive_ptr<pmt::pmt_base>)

I have Python 3.9.5, Slackware64-current, librtlsdr installed and working (the included
codes runs fine). SWIG is version 4.0.2.

The gr-osmosdr problem seems to be the only remaining issue.

Can anyone indicate me where to search?

John